1. Field of the Invention
The present invention relates to a screen printing machine and a stencil sheet assembly used in squeegee printing.
2. Description of the Related Art
As shown in Japanese Patent Publication No. 21733/1994, a conventional simplified printing machine used in squeegee printing is provided with a base member installed with printed matter and a block frame attached to the base member such that an interval between the block frame and the base member is adjustable. Further, the block frame is detachably attached with a stencil sheet assembly constituted by extending stencil sheet on a frame member. In printing operation, printed matter is mounted at a predetermined position on the base member, ink is placed on the stencil sheet and the stencil sheet is pushed downwardly and squeegeed. Thereby, pertinent tension is applied to the stencil sheet, the stencil sheet applied with the tension is brought into contact with the printed matter, ink is transcribed onto the printed matter and an image is formed.
In the case of the above-described structure, the tension applied to the stencil sheet by the squeegeeing operation does not become constant as a number of times of use increases, and skilled technique is needed to continue applying the pertinent tension stably. Further, the apparatus is large-scaled and the structure is complicated.
Further, when the tension is applied to the stencil sheet of the stencil sheet assembly, there is a concern that there causes destruction by peeling off an adhering agent for adhering the stencil sheet and the frame member and applied tension becomes unstable.
It is an object of the present invention to provide a screen printing machine and a stencil sheet assembly capable of firmly applying constant tension to stencil sheet by a simple structure.
According to a first aspect of the present invention, there is provided a screen printing machine comprising a stencil sheet assembly having a frame member having outer peripheral sides for partitioning an outer configuration and inner peripheral sides for partitioning an opening and stencil sheet adhered to one face of the frame member to cover the opening. Further, there is provided a tension frame projected to inner sides of the inner peripheral sides of the frame member, having a raised portion raised toward the stencil sheet and arranged on other face of the frame member for applying tension to the stencil sheet. Further, there is provided holding means for holding the tension frame and the stencil sheet assembly which are put together such that a front face of the tension frame in a direction of raising the raised portion and the other face of the frame member are brought into contact with each other.
According to a second aspect of the present invention, there is provided the screen printing machine according to the first aspect, wherein at least one folding groove portion in parallel with the inner peripheral sides of the frame member is formed on the other face of the frame member.
According to a third aspect of the present invention, there is provided a stencil sheet assembly comprising a frame member having outer peripheral sides for partitioning an outer configuration and inner peripheral sides for partitioning an opening, stencil sheet adhered to one face of the frame member to cover the opening, and at least one folding groove portion formed on other face of the frame member and in parallel with the inner peripheral sides of the frame member.
According to a fourth aspect of the present invention, there is provided the stencil sheet assembly according to the third aspect wherein the frame member is a frame member substantially in a rectangular shape having four of the outer peripheral sides and four of the inner peripheral sides and the opening substantially in a rectangular shape, wherein the folding groove portion comprises four of folding groove portions formed along the four inner peripheral sides, and wherein four corners of the inner peripheral sides of the frame member are formed with cut-in portions reaching intersecting points of the folding groove portions orthogonally intersecting with each other and contiguous to each other.